The dispute arose from the state of Kansas's requirement, passed in April 2011, that residents must provide documentary proof of citizenship to vote in state and federal elections. Accepted documents included birth certificates or passports.

The League of Women Voters of Kansas, along with a handful of others, sued the state in February in the District of Kansas federal court, claiming they had been wrongfully denied the right to vote under the National Voter Registration Act because they failed to supply eligible documents upon registration.

While Kansas Secretary of State Kris Kobach argued that "the NVRA did not speak to or preempt" documentary proof of citizenship requirements, the District of Kansas granted the voters' motion for a preliminary injunction against the enforcement of the policy. This allowed 18,000 Kansas votes that had originally been barred to count in the state's Aug. 2 presidential primary.

Dale Ho of the ACLU, representing the plaintiffs, asked the 10th Circuit to uphold the district court's ruling at a hearing on Aug. 23. Ho argued that Kansas was forcing voters to adhere to stricter registration guidelines than those of surrounding states.

"The record case shows that in fact 18,000 Kansans were blocked from registering to vote," Ho said. "People who, if they lived in any other states ... likely would have been registered without a second thought."

In the 85-page opinion penned by U.S. Circuit Judge Jerome Holmes, the three-judge panel agreed.

"The district court found that several of the named plaintiffs had registered in 2013 or 2014 to vote in the 2014 elections and that they desired to vote in the upcoming 2016 elections," the opinion says.

"Further, as of March 2016, 12,717 applications had been cancelled since Kansas's [documentary proof of citizenship] requirement went into effect and another 5,655 applications were suspended as incomplete.

"In other words, over 18,000 Kansans stood to lose the right to vote in the coming general elections—elections that are less than one month away."

The circuit panel agreed with the lower court that the NVRA explicitly allows American voters to submit their vote by supplying only the "minimum amount of information necessary," which does not include documentary proof of citizenship.

Kobach, whose office did not return a request for comment, continues to stand behind the policy, arguing that non-citizens could possibly disrupt the election process without proper voter registration vetting.

But Holmes dismissed this anxiety in the panel's written opinion.

"Exceedingly few non-citizens have been shown to have voted compared to the number of Kansans who stand to lose the right to vote in the coming elections," he wrote.

"The public interest in broad exercise of the right to vote will be furthered rather than harmed by the district court's injunction," he added.